1. Field of the Invention
The present invention pertains to systems and methods for controlling liquid outflow from a liquid-gas separator to improve accuracy of measuring oil production from wells which produce mostly water.
2. Background
Production from wells which are likely to produce significant amounts of water poses certain problems in measuring the net oil content of the production stream. Typically, a well may produce fluids which are collected in a separator tank for separating gas from the liquid flow stream and wherein the liquid flow stream is then conducted through a meter for measuring the water content of the liquid mixture (the so-called "watercut") and a flow meter for measuring the total liquid flow rate. In such arrangements, the net oil production in the flow stream, when passed through the watercut meter, provides highly inaccurate measurements of net oil flow.
For example, in marginally economic and so-called "high watercut" oil production wells, the identification of the net oil production is difficult because the accuracy of measurement of the water content of the flow stream is particularly low in arrangements where a conventional two-phase separator uses a liquid dump valve which periodically releases a fixed volume of liquid. In such arrangements, flow rates and watercut are measured continuously as each slug or fixed volume of liquid passes through the respective meters. In wells wherein only a relatively thin layer of oil accumulates in the separator vessel above the water prior to being dumped, the accuracy of measuring the net oil production is relatively low. The watercut meter must respond virtually instantaneously to a large change in the water content of the mixture, and the flow rate, from near one hundred percent (100%) to near zero percent (0%) water content, for example. It is not uncommon to experience at least a ten percent (10%) error in net oil production measured with conventional arrangements. The present invention overcomes this problem with a unique flow control system used in combination with a separator vessel for receiving the well production flowstream. Improving the oil metering accuracy for high watercut wells will allow more accurate discrimination about which wells are still economic and which should be shut in.